DOMPurify – how to keep (sub)strong tags included in a deleted(unwanted) span tag?

I use DOMPurify library (https://github.com/cure53/DOMPurify) to clean up html code copied from google docs.

I would like to remove the span tags from the copied text but keep the text inside the tags as well as any strong tags included in the deleted span tags.

I manage to remove the span tags while keeping the text inside the tags but any strong tags are also removed.

Example

DOMPurify.sanitize("<p>
<span style="background-color:transparent;color:#000000;"><strong>Some strong text</strong></span>
</p>", {
    ALLOWED_TAGS: ['p','strong']
})

Output

<p>Some strong text</p>

Expected output

<p><strong>Some strong text</strong></p>

I also tried with this kind of hook

DOMPurify.addHook("afterSanitizeAttributes", function (node, data, config) {
  if (node.nodeName === "SPAN") {
    node.replaceWith(node.textContent ?? "");
  }
});

But the output is the same, <strong> tags inside <span> are also deleted.

Can you please help me to keep (sub) <strong> tags after “sanitize”?

Many thanks